There are many situations in which it is desired to operate a crane hoist with means for safely lifting loads from the deck of a heaving work boat with a crane mounted on an offshore vessel, pipe-lay vessel or nonfloating platform. This is accomplished by allowing the crane hook to follow the heaving motion of a load on the deck of a work boat at a low level of pre-tension on the hoist cable which also reduces shock loads under full load dynamic conditions. Various means for keeping slack out of the line have been implemented, such as a spring connected between a sheave carrying the line and a stationary point, a counterweight attached to one or more sheaves in the line which continually imposes a pre-tension to take out any slack, various arrangements of line shorteners using hydraulic rams, etc. Control of crane hoists having such compensation means have generally either been expensive and complicated or have relied heavily on the crane operator to judge visually when to lift the load from the heaving deck. This places a heavy burden on the crane operator since any errors in judgment could result in causing the operator to attempt to lift the load at the worst possible instant, such as while the deck is moving downwardly at the same time there is still slack in the line. Pulling up on the load at such an instant could result in a heavy jerk, placing extremely heavy instantaneous loads on the attached cable, derrick boom and other parts of the system. Thus, it would be desirable to provide a relatively simple, reliable and straightforward control system which would assist the crane operator in determining the optimum time to lift the load and which would also operate to avoid the imposition of peak loads even in the case of an attempt to lift the load at an inopportune time.